Display device

Abstract

A display device that senses externally applied pressure and a change in the resonant frequency of a piezoelectric element. The display device includes a piezoelectric sensor layer including a piezoelectric sensor; and a display panel disposed on the piezoelectric sensor layer. The piezoelectric sensor includes: a piezoelectric element having a first electrode, a second electrode facing the first electrode, and a piezoelectric material disposed between the first electrode and the second electrode; an alternating current (AC) voltage generator connected to the first electrode and applies a voltage having a resonance frequency to the piezoelectric element. A sensing circuit connected to the second electrode is configured to measure a change in impedance of the piezoelectric element.

What is claimed is: 
     
         1 . A display device comprising:
 a piezoelectric sensor layer including a piezoelectric sensor comprising a piezoelectric element; and   a display panel disposed on the piezoelectric sensor layer,   wherein the piezoelectric sensor includes a sensing circuit connected to the piezoelectric element, and wherein the sensing circuit is configured to measure a change in impedance of the piezoelectric element when an alternating current (AC) voltage having a resonance frequency of the piezoelectric element is input to the piezoelectric element.   
     
     
         2 . The display device of  claim 1 , wherein the piezoelectric element of the piezoelectric sensor comprises a first electrode, a second electrode facing the first electrode, and a piezoelectric material disposed between the first electrode and the second electrode; and
 wherein the piezoelectric sensor further includes an AC voltage generator connected to the first electrode, the AC voltage generator configured to provide the AC voltage having the resonance frequency to the piezoelectric element.   
     
     
         3 . The display device of  claim 2 , wherein the sensing circuit comprises:
 a first node connected to the second electrode;   a sensing resistor and an amplifier connected to the first node; and   an analog-to-digital converter connected to the amplifier.   
     
     
         4 . The display device of  claim 3 , further comprising a rectifier circuit electrically connected between the amplifier and the analog-to-digital converter. 
     
     
         5 . The display device of  claim 1 , wherein an impedance value of the piezoelectric element increases when an external pressure on the display panel increases. 
     
     
         6 . The display device of  claim 1 , wherein the piezoelectric sensor layer further comprises:
 a base film having the piezoelectric element disposed thereon;   a pad disposed on the base film; and   an input line connecting the pad and the piezoelectric element.   
     
     
         7 . The display device according to  claim 6 , wherein the piezoelectric element comprises a plurality of piezoelectric elements disposed on the base film in an array. 
     
     
         8 . The display device of  claim 6 , wherein the display panel includes a driving integrated circuit, and the pad is electrically connected to the driving integrated circuit. 
     
     
         9 . The display device of  claim 8 , wherein the driving integrated circuit comprises a plurality of analog-to-digital converters, and the piezoelectric element is connected to the analog-to-digital converters. 
     
     
         10 . The display device of  claim 1 , further comprising an input sensing unit disposed on the display panel. 
     
     
         11 . The display device of  claim 1 , further comprising a window disposed on the display panel. 
     
     
         12 . The display panel of  claim 11 , wherein the window is comprised of a material that transmits an externally applied pressure to the piezoelectric element. 
     
     
         13 . The display device of  claim 1 , wherein the display panel includes a plurality of pixels, and each of the pixels comprises a pixel electrode, a common electrode facing the pixel electrode, and an organic light emitting layer disposed between the pixel electrode and the common electrode. 
     
     
         14 . A display device comprising:
 a piezoelectric sensor layer including a piezoelectric sensor; and   a display panel disposed on the piezoelectric sensor layer,   wherein the piezoelectric sensor comprises:   a transmitter comprising a first piezoelectric element and an alternating current (AC) voltage generator configured to provide a voltage having a resonance frequency to the first piezoelectric element; and   a receiver comprising a second piezoelectric element, and a sensing circuit configured to measure a current generated from the second piezoelectric element.   
     
     
         15 . The display device of  claim 14 , wherein the first piezoelectric element generates an ultrasonic signal when the voltage having the resonance frequency is provided to the first piezoelectric element. 
     
     
         16 . The display device of  claim 15 , wherein the ultrasonic signal is reflected after hitting an object, and the second piezoelectric element receives the reflected signal to generate a current. 
     
     
         17 . The display device of  claim 16 , further comprising a controller connected to the sensing circuit, wherein, when the transmitter transmits the ultrasonic signal, the receiver receives the reflected signal after a first time, and the controller is configured to calculate a vertical distance between the object and the display device based on the first time. 
     
     
         18 . The display device of  claim 14 , wherein the piezoelectric sensor layer comprises a base film and a plurality of piezoelectric elements disposed on the base film along a plurality of columns and a plurality of rows. 
     
     
         19 . The display device of  claim 18 , further comprising a controller connected to the sensing circuit, wherein the piezoelectric sensor comprises a plurality of receivers configured to collect position information of an object, and the controller is configured to map the position information of the object on an x-y plane. 
     
     
         20 . The display device of  claim 19 , wherein the controller is configured to calculate a horizontal movement distance of the object based on the position information of the object. 
     
     
         21 . The display device of  claim 14 , wherein the first piezoelectric element and the second piezoelectric element are integrated. 
     
     
         22 . A display device comprising:
 a piezoelectric sensor layer comprising a piezoelectric sensor; and   a display panel disposed on the piezoelectric sensor layer,   wherein the piezoelectric sensor comprises:   a piezoelectric element comprising a first electrode, a second electrode facing the first electrode, and a piezoelectric material disposed between the first electrode and the second electrode;   an alternating current (AC) voltage generator connected to the first electrode and configured to provide a voltage having a variable frequency to the piezoelectric element; and   a sensing circuit connected to the second electrode and configured to measure a change in a resonance frequency of the piezoelectric element.   
     
     
         23 . The display device of  claim 22 , wherein the sensing circuit is configured to measure a first resonance frequency having a lowest impedance value among a plurality of frequencies in a state where no pressure is applied to the piezoelectric element, and to measure a second resonance frequency having the lowest impedance value among a plurality of frequencies in a state where pressure is applied to the piezoelectric element, wherein the first resonance frequency and the second resonance frequency are different from each other.